Distribution of TH (+) and NPV (+) Nerve Fibers and Neurons in Human Choroidal Whole–Mounts

Abstract

Abstract: : Purpose:To determine the presence of NPY (+) and TH (+) nerve fibers and intrinsic choroidal neurons (ICNs) in human. Methods: Twenty human choroidal whole mounts were processed for indirect immunofluorescence. Antibody to a component of the neuronal cytoskeleton, neurofilament 200 kDa (NF–200), was combined with antibodies to tyroxine hydroxylase (TH) and antibodies to neuropeptide Y (NPY). Results: TH(+) and NPY (+) fibers were distributed at three different levels: suprachoroid–large size vessel layer, and two different depths of the medium size vessel layer. On reaching the vessel wall, NPY (+) and TH (+) perivascular axons exhibited small terminal dilations whose morphology varied. NPY (+) and TH(+) ICNs were observed in the suprachoroid. In addition, TH (+) ICNs were located at the medium size vessel layer. Overall, NPY (+) and TH(+) ICNs were more frequent in the temporal central area, both in isolation and forming microganglia. We also observed small, intensely immunoreactive (IR) TH(+)/NF200(–) spindle elements. These THIR elements were mainly distributed in the suprachoroid, from the equator to the periphery. Conclusions:The human choroid contains an abundance of NPY (+) and TH (+) nerve fibers associated with chroroidal vascular structures. NPY (+) and TH(+) innervation could contribute to blood flow regulation. It is possible that the existence of NPY (+) and TH(+) ICNs contributes to choroidal self–regulation as proposed. The preferential location of these cells in the submacular area suggests the possibility that dysfunction or degeneration of these cells could be a factor in vascular pathologies observed in ocular disease, such as diabetic macular edema or age related macular degeneration.

Keywords: innervation: neural regulation • choroid • immunohistochemistry